CODEWITHSUNDEEP
javascript
Julian Hollmann
Julian Hollmann

Reputation: 2912

Parse object dot notation to retrieve a value of an object

I'm finding myself struggling with a little problem. Let's say I've got an object:

var foo = {
    bar: {
        baz: true
    }
};

Now I also have a String 'foo.bar.baz'. I'd now like to retrieve the value from the object using the string.

Please note: This is just an example, the solution needs to be dynamic.

Update:

I need the variable name also to be dynamic and parsed from the string. Also I can't be sure that my variable is a property of the window.

I have already built a solution using eval, but this is pretty ugly I think: http://jsfiddle.net/vvzyX/

Upvotes: 0

Views: 1913

Answers (4)

Minko Gechev
Minko Gechev

Reputation: 25682

Here is how you can do this:

function getValue(namespace, parent) {
    var parts = namespace.split('.'),
        current = parent || window;
    for (var i = 0; i < parts.length; i += 1) {
        if (current[parts[i]]) {
            current = current[parts[i]];
        } else {
          if (i >= parts.length - 1)
            return undefined;
        }
    }
    return current;
}
var foo = {
    bar: {
        baz: true
    }
};
console.log(getValue('foo.bar.baz')); //true

The first argument of the function is the namespace (dot separated values) and the second one is the parent object, if parent is not provided then window is used.

One more example using the parent argument:

var str = 'foo.bar.baz';
    foo = {
       bar: {
          baz: true
       }
    };

result = getValue(str, foo);
console.log(result);

Here is an example in jsfiddle.

Similar approach is used in YUI. Their approach is called Namespace pattern. The main benefit is simulation of packages/namespaces. The only difference between this script and the namespace pattern is that the namespace function creates nested structure instead of only returning value.

Upvotes: 2

Amberlamps
Amberlamps

Reputation: 40488

Try this:

var name = [window].concat('foo.bar.baz'.split('.')).reduce(function(prev, curr) {
    return prev[curr];
});

console.log(name);

// -> 'true'

Upvotes: 2

georg
georg

Reputation: 215009

For example,

function get(obj, path) {
    return path.split('.').reduce(function(obj, p) {
        return obj[p]
    }, obj);
}

Demo:

tree = {
    foo: {
        bar: 1,
        baz: { quux: 3 },
    },
    spam: 1
}

console.log(get(tree, 'foo.baz.quux')) // 3

Upvotes: 4

Simon Wang
Simon Wang

Reputation: 2943

What I can think of is using string split to split that string into an array first, and access the object via [] to access the attribute of that object with a loop

Upvotes: 0

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